PROJECT SUMMARY/ABSTRACT These studies are designed to test the novel idea that Sprouty-2 (SPRY2), an intracellular regulator of receptor tyrosine kinase-induced signaling, is a central gatekeeper restricting colonic epithelial repair responses including protective changes in secretory differentiation and wound healing. Our preliminary data show that SPRY2 is downregulated by inflammation in the colonic epithelium. This appears to be a protective or compensatory response, as mice with intestinal epithelium-specific SPRY2 deletion are resistant to dextran sulfate sodium (DSS)-induced colitis. Furthermore, these mice display altered intracellular signaling, elevated interleukin IL-33 levels, more tuft cells, and increased mucus production. Thus, a regulated loss of SPRY2 may be an important, potentially exploitable, mechanism contributing to repair of the colonic epithelial barrier following an insult. In this project, we will test the hypothesis that colitis-induced loss of SPRY2 releases normal homeostatic inhibition of intracellular signaling to promote protective epithelial and epithelial- mesenchymal responses. Aims of the study are (1) define the influence of SPRY2 on colonic secretory cell differentiation and function; (2) test the role of SPRY2 in epithelial wound repair, and (3) determine whether SPRY2 downregulation drives recovery from colitis. We will test the central hypothesis with coordinated in vitro and in vivo models including human and mouse primary colonic epithelial culture, cell culture models, and in vivo colitis using conditional knockout mice or mice in which SPRY2 levels are manipulated through nanoparticle-delivered expression constructs.